In article <4uponn$5vn$1@sydney.DIALix.oz.au>,
John Savage <koala@sydney.dialix.com.au> wrote:>lrudolph@panix.com (Lee Rudolph) writes:>>In brief, Diamond's claims are that "between 5 and 30 percent of>>American and British babies [have been] adulterously conceived",>>This was discussed on a recent episode of the ABC Science Show, but>as so often happens, I'm afraid I paid less attention to the program>than it rightly deserves. Anyway, I think the ballpark figure they used>was that around 10% of children do not belong genetically to the man>they believe to be their father.

I just picked up Timothy Taylor's _The Prehistory of Sex: Four Million
Years of Human Sexual Culture_ (Bantam: 1996). Here's his summarization of
the subject:

(pp 77-79)
"...In tests of genetic paternity recently conducted by Robin Baker and
Mark Bellis [1], they found that around 10 percent of children had been
sired by someone other than their ostensible fathers -- although the
fathers consciously believed these children to be their own.

" Baker and Bellis believe that male biological mechanisms are geared
to the expectation of cuckoldry. Human males have relatively large
testicles and produce far more sperm than they seem to need. In normal
conception a single egg is fertilized by a single sperm. So what are the
other 2,249,999 sperm from an average 2.25-million-sperm ejaculation up
to? Humans (along with other species such as chimpanzees and lion),
Baker and Bellis argue, have evolved a system of sperm competition in
which the majorityof sperm actually make no attempt to find the egg.
Rather, these sperm are on anti-cuckolding duty. Some wait around ready
to attacka lien sperm, while others -- whose tails seem deliberately
deformed -- knot together to form a passive tangled barrier against any
intruders. If a man spends an entire day with his female partner, then
has sexual intercourse with her, he ejaculates far fewer sperm than he
would have had he spent the day apart from her -- a period with
opportunites for her to be unfaithful. Nevertheless, although the man's
sperm may battle it out, it may ultimately be the woman's internal
manipulation of sperm via orgasm during intercourse and subsequent
masturbation that most influences whose baby she will have (see Chapter 2)[1]

" What motivation could the women in B and B's study have for
cuckolding their husbands at arate of one in ten? Matt Ridley interprets
their case in stark sociobiological terms, citing the work of Anders
Moller.[3] Moller, a zoologist, has found that the more physically
attractive a male swallow is, the less parental investment he makes in
his offspring; female swallows are thus encouraged to find a
mediocre-looking but caring partner and to cuckold him. Humans may do
this too, Ridley suggests -- a woman may marry a rich but ugly man but
take a handsome lover. But what he does not explain is why a woman would
wish to concieve by her handsome lover. Surely her children would be
better off, in a society that ultimately values wealth, having the genes
of the rich man. It may be that people and society are inclear about
what they value most; nevertheless, it seems unlikely that B and B's
one-in-ten cuckoo-in-the-nest children can be explained in purely
sociobiological terms.

" Liverpool, where B and B conducted their survey, is an
international seaport that, since the industrial revolution, has seen
hordes of seamen and laborares come and go. Whether Liverpudlian
traditions of marital fidelity and uncertaind paternity closely mirror
those of say, Salt Lake City or Stockholm or even many other parts of
Britain, is debatable. But even accepting the statistics at face value,
the researcher's conclusions are not foolproof. A woman's chances of
concieveing with a lover whom she has actually chosen purely for sexual
pleasure are rather high for a set of rather mundane and practical
reasons: cheating lovers do not want to be caught carrying condoms or
diaphragms, or the sex might be opportunistic or a chance, drunken
encounter."

[2 Baker and Bellis studied the way women can manipulate sperm within
their bodies, rejecting it ("flowback") when they do not want to concieve
and sucking it up ("up-suck") when they do. B and B are convinced that
fmale masturbation plays and important part in the process, generating
uterine contractions that help a woman to keep a particular man's sperm
in play for several days after intercourse. The control of orgasm and
up-suck also allows a woman with more than one partner to have a
surprising measure of control of whom she concieves by. (pg 61)

Anyway, whether or not the 10% figure is accurate, it seems from recent
disocveries in this area that humans are evolved to compete with each
other not just on the macro level, but on the cellular sperm-and-egg
level, which would seem to suggest a propensity for extramarital sex or
sex with multiple partners. Just the other night I watched a show on The
Learning Channel called "Why Sex" (or was it the show the night before?
at any rate, it was about the biology of sexual behavior) that said human
sperm, like that of several other animals, in addition to having
individual sperm cells specialize in blocking and destroying "alien"
sperm, thickens and forms a soft plug in the vaginal tract, which helps
to block any new deposits of sperm made. There is also a biological
adaptation to get around that: the human penis is shaped in such a way
to "ram" through a soft plug and, with the accompanying thrusting
motions, to pull a lot of it away from the opening of the cervix.

Again, not a mention of whther the 10%-children-fathered-extramaritally
figure is correct, but judging by just the biological adaptation humans
have, I wouldn't be at all surprised if the figure was accurate, or even
too low. (Diamond states, I think, that the blood typing done on the
children produced a figure of *at least* 10% fathered extramaritally, but
could not take into account the cases where the child inherited the
mother's blood factor or where the biological father had the same type of
blood factor as the mother's husband, so the true figure was at the time
impossible to calculate.)

--Stephanie

--
sfolse@odin.cair.du.edu <*> http://phoebe.cair.du.edu/~sfolse/
"Assiduous and frequent questioning is indeed the first key to wisdom ...for
by doubting we come to inquiry; through inquiring we perceive the truth..."
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